Apparatus and method for manufacturing a catalytic converter

ABSTRACT

Disclosed herein is a method of making a catalytic converter; forming a shell having a welding deformation detail; inserting and housing a catalyst substrate inside the shell, wherein a mat support material is disposed between the shell and the catalyst substrate; welding an end cone having a flange to the shell by applying a deformation force to the flange causing deformation of welding deformation detail.

RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS

This application is a divisional of U.S. Ser. No. 10/465,356, filed Jun.18, 2003.

BACKGROUND

Catalytic converters have been employed to catalyze exhaust fluids invehicles for more than twenty years and have been manufactured in anumber of ways. Catalytic converters play a critical role in ensuringthat fuel rich fluids are reduced down to acceptable levels, and are acomparatively expensive article within an exhaust system. The materialsare expensive, and manufacture is labor intensive. Furthermore, designpackages that increase durability and improve overall system performancefor reductions in emissions are at a premium. Accordingly, methods ofmanufacture have been put forth in attempts to reduce manufacturingcosts, while at the same time, increasing durability and stabilizingsystem performance.

One method of manufacturing catalytic converters is to provide apre-made canister and stuff it with the catalyst substrate and theinsulation/support pad. In this method, the catalyst substrate iswrapped with an intumescent or non-intumescent mat of a selectedthickness and weight (various weights are employed for variousapplications and desired properties). Generally, the wrapped substratematerial will create an assembly having outer dimensions that measureabout 8 mm larger than the inside dimensions of the converter shell orcanister. The assembly as described is then forced through a reductioncone and into the converter shell. Up to about 20,000 lbs of force maybe used to accomplish the insertion of the assembly into the can. Moreparticularly, within this range a force up to 7,000 lbs may be used. Themethod is costly.

A catalytic converter may be produced by a method referred to as “thetourniquet method.” The tourniquet method dispenses with the reducingcone and thus avoids the high insertion pressures on the substrate andmat materials. The method places the substrate and mat assembly into acanister open on one longitudinal edge. The canister is closed aroundthe assembly by straps and compressed to the desired size. The open endsof the canister will, in this position, be overlapping and then arewelded together. This method is also expensive and labor intensive.Further, due to this overlap, engineering design consideration must begiven to the space alteration inside the canister due to the overlappededge. The overlapped edge causes a mat density change in the local areaof the overlap. This is a further cost addition.

Further, both of the above described catalyst and shell assemblies mayhave transitional areas to accommodate any difference in diameterbetween the catalyst shell diameter and the diameter of inlet and outletpipes. These transitions, e.g., endcones, may be affixed to the shell byMetal Inert Gas (MIG) welding, which may result in a significant amountof cycle time and heat addition to the parts. An alternative to MIGwelding is spinforming of the ends of a shell that extends beyond theends of the catalyst. This process is also high in cycle time and alsoresults in parts having a large area of heated surface. Accordingly,there remains a need in the art for a catalytic converter that is easilyand inexpensively manufactured, that increases durability, and does notrestrict design choice.

SUMMARY

Disclosed herein is a catalytic converter including a shell having awelding deformation detail; a catalyst substrate inserted within theshell; a mat support material disposed between the catalyst substrateand the shell; an end cone having a flange; and wherein the flange isdeformation welded to the shell at the welding deformation detail.

Further disclosed herein is a method of making a catalytic converterincluding forming a shell having a welding deformation detail; insertingand housing a catalyst substrate inside the shell, wherein a mat supportmaterial is disposed between the shell and the catalyst substrate;welding an end cone having a flange to the shell by applying adeformation force to the flange causing deformation of weldingdeformation detail.

The above-described and other features will be appreciated andunderstood by those skilled in the art from the following detaileddescription, drawings, and appended claims.

DRAWINGS

Referring now to the figures, which are exemplary embodiments, andwherein the like elements are numbered alike:

FIG. 1 is a partial cross-sectional view of a catalytic converterembodiment comprising an annular deformation resistance weld at theinterface between converter shell and end cone.

FIG. 2 is a partial cross-sectional view of an embodiment comprising amat support protection surface formed by a shell portion.

FIG. 3 is a partial cross-sectional view of an embodiment comprising amat support protection surface formed by an extended flange portion ofan end cone.

FIG. 4 is a partial cross-sectional view of an embodiment comprising anendplate.

FIG. 5 is a partial cross-sectional view of an embodiment comprising atube, and further depicting an insulating space between an inner andouter cone.

FIG. 6 is a partial cross-sectional view of an embodiment comprising aflared snorkel to tube weld interface illustrating the proposed ADRWjoining method.

FIG. 7 is a partial cross-sectional view of an embodiment comprising amat protection surface formed by a curled portion of the shell.

FIG. 8 is a partial cross-sectional view of an embodiment comprising aflared shell.

FIG. 9 is a partial cross-sectional view of an embodiment comprising aninsulating space between an end cone and an inner cone, wherein the endcone is spot welded to the shell.

FIG. 10 is a cross-sectional view of an end portion of an end conecomprising tab portions.

FIG. 11 is a partial cross-sectional view an embodiment comprising aconcave rib portion at the weld interface.

FIG. 12 is a partial cross-sectional view of an embodiment comprisingtwo catalysts.

DETAILED DESCRIPTION

A method of welding end-cones to a converter assembly is describedbelow. Although the method is described in relation to welding end-conesto a converter assembly, this method may also be used in other weldingapplications, e.g., tube to tube, converter to tube, and the like.

Annular Deformation Resistance Welding (ADRW), as used herein, refersgenerally to a welding method, wherein a joint is formed through thedeformation and displacement of material at the weld interface. AnnularDeformation Resistance Welding is also described in U.S. Pat. No.6,552,294 to Ananthanarayanan et al., which is herein incorporated byreference. Although ADRW is similar to “Resistance Welding,” it is adistinct welding method as will be discussed in greater detail.Resistance welding, as used herein, refers generally to a method used tojoin metallic parts with electric current. There are several forms ofresistance welding, including, for example, spot welding, seam selding,projection welding, butt welding, and the like. In all forms ofresistance welding, the parts are locally heated until a molten poolforms. The parts are then allowed to cool, and the pool solidifies toform a weld bond. Generally, during resistance welding, an operator ofresistance welding equipment has control over, for example, currentsetting, electrode force, and weld time.

In resistance welding, heat is created by electrode(s) passing anelectric current through the work pieces. The heat generated may dependon electrical resistance and thermal conductivity of the metal, and thetime that the current is applied. The heat generated may be expressed bythe following equation:E=I ² ·R·twhere E is the heat energy, I is the current, R is the electricalresistance and t is the time that the current is applied. Copper may beused for electrodes, because it has a low resistance and high thermalconductivity compared to most metals. This promotes heat generation inthe work pieces instead of the electrodes. The electrodes may be cooledwith water, removing excess heat, to prevent the electrodes fromoverheating.

Furthermore, in resistance welding, the electrodes are held under acontrolled force during welding. The resistance across the interfacesbetween the work pieces and the electrodes may be affected by the amountof the force applied. The force may be adjusted to immediately createheat at the interface between the work pieces. Moreover, if the force istoo low expulsion, weld splash, and/or the like can occur. The heat usedto produce the molten pool may depend on, for example, the thermalconductivity and melting point of the metal being welded. A materialwith a relatively high thermal conductivity will quickly conduct heataway from the weld pool, thus increasing the total heat used to melt thepool compared to a material with a relatively low melting point.

In ADRW, at least one of the work pieces comprises a deformation detail,for example, a rib portion, wherein welding occurs at the deformationdetail. As will be discussed in greater detail, the deformation detailfacilitates deformation under a deformation force. Like simpleresistance welding, an electrode is applied to the work piece. Forexample, a current of about 5,000 amperes to about 20,000 amperes isapplied for less than 1 second. More particularly, a current of about15,000 amperes to 20,000 amperes is used. Further, the electrode(s)apply a force of about 300 to 800 pounds to the work piece. Unlikesimple resistance welding, however, in ADRW, the force applied by theelectrode causes deformation of the deformation detail. For example, ifthe deformation detail is a rib portion, the force applied by theelectrode causes the rib to compress, i.e., deform. Furthermore, thewelding surfaces are deformed under the heat generated by the currentacross the welding surfaces and the force of the electrodes. A weld bondis formed while the materials are in this plastic-like state, whichallows impurities in the metal to be displaced away from the weld bondas the welding surfaces are placed in intimate contact with each otherunder the electrode force. In other words, impurities are pushedradially away from the weld area, i.e., the material is ejected awayfrom the area that forms the weld bond, allowing for a metal-to-metalweld bond relatively free of contaminates. In the ADRW method, thedeformation has an action linear distance about equal to the desiredweld bond. For example, the weld bond is about equal to the thickness ofone material thickness in order to be of equal load bearing capacity asthe parent material.

Further, the deformation detail is not limited to embodiments depictinga rib portion; rather the deformation detail may be a detail (i.e.,feature) that facilitates deformation as described above. Moreover, theADRW method may be used to create leak-tight joints with uniformcircumferential weld strength. The term “leak-tight”, as used herein,refers to a joint that generally prohibits the passage of fluidtherethrough.

Additionally, the heat-affected zone of the weld in the ADRW method ismuch smaller, resulting in less strength reduction of the parentmaterials when compared to, for example, Gas Metal Arc Welding (GMAW),and the like. GMAW may also be referred to as Metal Inert Gas (MIG)welding. In MIG welding the “inert gas” refers to a shielding gas, whichis generally supplied from a cylinder or other gas source and then pipedto the welding gun. Further, a metal wire is used to start the arc, andthen is fed into the puddle of molten metal to continuously replenishthe metal in the puddle that is used to join the materials.

The ADRW method allows the weld to be monitored to indicate quality ofthe finished product, which is advantageous in that it may reduce weldrepair, and may have potential for reducing capital expenditure forinspection equipment (e.g., elimination of leak tester). Moreover, thismethod may reduce cycle time to less than about 5 seconds and even acycle time of about 1 second (s) in some embodiments. Thus, an increasedcapacity of a production cell may be realized, while using substantiallythe same capital.

Several combinations of catalytic converters are discussed hereunderwith reference to individual drawing figures. One of skill in the artwill easily recognize that many of the components of each of theembodiments are similar or identical to the others. Each of theseelements is introduced in the discussion of FIG. 1, but is not repeatedfor each embodiment. Distinct structure is discussed relative to eachfigure/embodiments.

Referring now to FIG. 1, an exemplary catalytic converter embodimentgenerally designated 10 is illustrated. Catalytic converter 10 comprisesa catalyst substrate 12 inserted and housed within a shell 16 with a matsupport material 14 disposed therebetween. A subassembly is formed whenmat support material 14 is wrapped around catalyst substrate 12. Shell16 is disposed around mat support material 14 and is sized and shapeddepending on the size and shape of the subassembly. Shell 16 comprises ashell rib portion 18 having a surface area sufficient to provide awelding interface with an end cone 20.

End cone 20 comprises an opening 22, a flange 24, and an inner cone 26.As will be discussed in greater detail, end cone 20 is joined to shell16 at ribbed portion 18 using the ADRW method. End cone 20 is blanked,i.e., the sheet metal forming process by which the part is removed fromthe strip of parent metal. This blanking process leaves flange 24, whichthen fits over shell 16, wherein ribbed portion 18 of shell 16 abutsflange 24 of end cone 20. Since end cone 20 is cut from the parent metalby blanking instead of blanking and pinch trimming a comparatively moresimple end cone 20 form may be used. The term “pinch trimming” as usedherein refers an additional process where a flange (e.g., 24), which isformed by a previous blanking process is then pushed through anadditional die detail that wipes the short flange, left from blanking,along the centerline leaving a longer skirt. This type of endcone may beused, for example, on stuffed shells. Flange 24 comprises a matingsurface sufficient for an electrode (not shown). During the ADRW method,an electrode applies a force to flange 24, wherein deformation occurs inthe weld area under the force and heat generated by the current flowacross the interface from rib portion 18 to flange 24. Moreover, theforce applied by the electrode is sufficient to cause deformationbetween rib portion 18 and flange 24. The deformation is accomplished inFIG. 1 due to the mismatch in flatness of the two surfaces of ribportion 18 and flange 24 respectively. In other words, the two surfacesare not flat relative to one-another.

As mentioned above, the distinct elements of each embodiment arediscussed in each figure, for example, FIG. 2 illustrates a catalyticconverter embodiment generally designated 100 comprising a mat supportprotection surface 28. Mat protection surface 28 may be formed in thesame operation that creates shell rib portion 18. In other words, an endportion of shell 16 is used to form mat protection surface 28. Matprotection surface 28 may be used to shield mat support material 14 fromhigh temperature exhaust fluid, which may cause mat support material 14to overheat under certain high temperature conditions. Further, it maybe used to reduce the temperature of the outer surface of catalyticconverter 100 and/or to protect mat support material 14 from exhaustfluid erosion.

FIG. 3 illustrates a catalytic converter embodiment generally designated150 comprising a mat protection surface 30. Mat protection surface 30 isformed when flange 24 is welded to shell 16. In this embodiment, flange24 comprises an extended length parallel to the face of catalystsubstrate 12, forming mat protection surface 30. Similar to matprotection surface 28 depicted in FIG. 2, mat protection 30 may be usedto shield shell 16 from high temperature exhaust fluid, to reduce thetemperature of the outer surface of catalytic converter 150; and/or toprotect mat support material 14 from exhaust fluid erosion.

FIG. 4 illustrates a catalytic converter embodiment generally designated200 comprising an end plate 32. End plate 32 is joined to shell 16 usingthe ADRW method at the interface of shell rib portion 18 and the portionof end plate 32 abutting shell rib portion 18. In this embodiment, thecatalyst substrate 12 is spaced away from endplate 32 to ensure propergas flow in and out of the catalyst. Further, an inner ring (not shown)may be used to act as inner end cone for mat protection. Alternatively,a mat protection surface (not shown) like mat protection surface 28 ofFIG. 2 may be formed in the same operation that creates shell ribportion 18. This embodiment further illustrates that ADRW may be usedeven when there is a disparity in the thickness of materials beingwelded, e.g., end plate 32 is thicker than shell 18. If MIG welding isused instead of ADRW for this embodiment, a material sufficiently thick(e.g., greater than or equal to about 1.45 mm) is employed for shell 16.Converter designs produced using the ADRW method are capable of usingshell materials having a thickness less than about 1.5 mm, and even athickness of less than about 0.66 mm in some embodiments. In the case ofthese embodiments, it is envisioned that thinner material may be usedfor the shell 16 as stated. Therefore, a deformation and/or displacementof about 0.66 mm to about 1.5 mm would occur in that example equal toboth the parent material and weld bond.

FIG. 4 further depicts an inlet tube 34 comprising an opening 22 and aninlet tube rib portion 36 having a surface area sufficient to provide awelding interface with end plate 32. This embodiment illustrates thatADRW may be used to weld tubes to cones. In this example, deformationwill occur at the interface between end plate 32 and inlet tube ribportion 36.

FIG. 5 illustrates a catalytic converter embodiment generally designated250 comprising an insulating space 44. End cone 20 comprises a flange 24and a tube-side weld area 40. Inner-end cone 26 comprises a flange 38and a tube-side weld area 42. In this embodiment, flange 24 is welded toflange 38 of inner end cone 26 and flange 38 is welded to shell 16 atshell rib portion 18. Shell rib portion 18, end cone 20, and inner endcone 26 may be welded together at the same time. Similarly, an inlettube 34 may be joined to end cone 20 and inner end cone 26 in the samefashion, i.e., by the ADRW method. In this example, tube-side weld area40 of end cone 20, tube-side weld area 42 of inner end cone 26, and arib portion 36 of inlet tube 34 are welded together. When inner end cone26 is joined to shell 16 using ADRW, flange 38 having an extended lengthforms a mat protection surface 39. Furthermore, joining flange 24 andtube-side weld area 40 of end cone 20 to flange 38 and tube-side weldarea 42 of inner end cone 26 respectively as described above, a sealedpocket is formed, which creates an insulating space 44. Since thematerials being welded in these examples are full thickness, i.e., thematerials have not been thinned due to extrusion, they may have moreload bearing capacity compared to the thinned materials. Moreover, thesealed pocket advantageously allows the used of insulating materialsthat if otherwise left free to migrate could plug and/or contaminate thecatalyst.

Examples of suitable insulating materials include formed ceramic fibermaterials comprising vermiculite, refractory ceramic fibers, organicbinders, combinations thereof, and the like. The insulating material maybe a non-expanding ceramic material, an intumescent material, or amaterial comprising both. Examples of non-expanding ceramic fibermaterial includes, but is not limited to, ceramic materials such asthose sold under the trademarks “NEXTEL” and “SAFFIL” by the “3M”Company, Minneapolis, Minn., or those sold under the trademark,“FIBERFRAX” and “CC-MAX” by the Unifrax Co., Niagara Falls, N.Y., andthe like. Examples of intumescent ceramic material include, but is notlimited to, ceramic materials such as those sold under the trademark“INTERAM” by the “3M” Company, Minneapolis, Minn., as well as thoseintumescents which are also sold under the aforementioned “FIBERFRAX”trademark, as well as combinations thereof and others.

FIG. 6 illustrates a catalytic converter embodiment generally designated300 comprising a flared snorkel to tube weld interface. In thisembodiment, end cone 20 comprises a flared end portion 46. Flared endportion 46 abuts inlet tube rib portion 36. An electrode, as describedabove, may be used to join the interfaces being welded, i.e., flared endportion 46 and inlet tube rib portion 36. In this example, flared endportion 46 allows full thickness materials, i.e., materials that havenot been thinned due to extrusion, to be joined. Accordingly, they mayhave a higher load bearing capacity compared to the thinned materials,which are more common in end cones where the snorkel extrusion end edgeis the point where the adjoining tube is attached by MIG welding.

FIG. 7 illustrates a catalytic converter embodiment generally designated350 comprising a mat protection surface 49 formed by a curled portion 48of shell 16. Curled portion 48 protects the mat edge from, for example,erosion, allowing the elimination of the inner cone, which has thisfunction as well as others. End cone 20 comprises an opening 22, and anangled welding interface 50, wherein the angled welding interface 50 hasan angle of about 10 degrees to about 45 degrees relative shell 16surface. Within this range, it is also desirable to have an angle ofabout 30 degrees to about 45 degrees. In this embodiment, thedeformation detail is the angled welding interface 50. In using the ADRWmethod, curled portion 48 abuts angled welding interface 50. Deformationwill occur at the interface between curled portion 48 and angled weldinginterface 50, which aids in impurity rejection as described above.Moreover, curled portion 48 has a sufficient stiffness, such that oneelectrode is sufficient, i.e., the welding may be completed without theuse of a backup electrode.

FIG. 8 illustrates a catalytic converter embodiment generally designated400 comprising shell 16 having a flared end portion 52. An end cone 20comprises an opening 22 and curved end portion 54. End cone 20 may bejoined to shell 16 using the ADRW method. In other embodiments, end cone20 may further comprise an inner end cone (not shown). End cone 20 maybe slid inside the shell 16 at the end comprising flared end portion 52.In this embodiment, the deformation detail used in the ADRW method isthe flared end portion 52. In the ADRW method, deformation will occur atthe interface between end cone 20 and flared end portion 52.Advantageously, since end cone 20 is slid inside the flared area ofshell 16, the overall package diameter may be reduced compared todesigns where end cone 20 is lapped over shell 16.

FIG. 9 illustrates a catalytic converter embodiment generally designated450 comprising an insulating space 44 between end cone 20 and inner endcone 26. End cone 20 is spot welded at flange 24 at intervals that aresufficient to be robust against flexure due to low cycle fatigue causedby the mis-match in growth due to the temperature difference betweeninner cone 26 and end cone 20. However, the ADRW method is used to joinshell 16 to inner end cone 26. Flange 56 of inner end cone 26 abutsshell rib portion 18. The ADRW method is used to join these layerstogether. Deformation occurs at the weld area, i.e., the interfacebetween shell rib portion 18 and flange 56 of inner end cone 26. Aninsulating space 44 is created between end cone 20 and inner end cone 26as described. Advantageously, insulating space 44 may be filled with aninsulating material. Examples of suitable insulating materials includedformed ceramic fiber materials comprising vermiculite, refractoryceramic fibers, organic binders, combinations thereof, and the like. Theinsulating material may be a non-expanding ceramic material, anintumescent material, or a material comprising both. Examples ofnon-expanding ceramic fiber material include, but is not limited to,ceramic materials such as those sold under the trademarks “NEXTEL” and“SAFFIL” by the “3M” Company, Minneapolis, Minn., or those sold underthe trademark, “FIBERFRAX” and “CC-MAX” by the Unifrax Co., NiagaraFalls, N.Y., and the like. Examples of intumescent ceramic materialincludes, but is not limited to, ceramic materials such as those soldunder the trademark “INTERAM” by the “3M” Company, Minneapolis, Minn.,as well as those intumescents which are also sold under theaforementioned “FIBERFRAX” trademark, as well as combinations thereofand others.

Referring now to FIG. 10, a flange cross sectional area generallydesignated 500 is shown. In this exemplary embodiment, flange 500comprises a plurality of tabs 58, which allow for mismatch in thermalexpansion length due to temperature difference between an inner cone 26and an end cone 20. An end cone comprising flange 500 having a pluralityof tabs 58 may be applicable, for example, to end cone 20 of FIG. 9where the inner cone 26 forms the gas sealing surface and endcone 20encloses insulating area 44.

FIG. 11 illustrates a catalytic converter embodiment generallydesignated 550. In this exemplary embodiment, shell 16 has ribbedportion 18 disposed inward compared to the exemplary embodiment depictedin FIG. 1 where ribbed portion 18 is disposed outwardly. In other words,ribbed portion 18 may be concave, as depicted in FIG. 11, or convex, asdepicted in FIG. 1. Moreover, this exemplary embodiment has an overallpackage diameter less than that of the outwardly disposed ribbedportion. In joining end cone 20 to shell 16, ribbed portion 18 of shell16 abuts flange 24 of end cone 20. Flange 24 comprises a mating surfacesufficient for an electrode (not shown) to apply a pressure to createdeformation during the ADRW method.

FIG. 12 illustrates an exemplary embodiment generally designated 600comprising a first canned portion 602 and a second canned portion 604.First canned portion 602 comprises a catalyst substrate 612 inserted andhoused within a shell 616 with a mat support material 614 disposedtherebetween, and a rib portion 618 (i.e., deformation detail). Secondcanned portion 604 comprises a catalyst substrate 612 inserted andhoused within a shell 616 with a mat support material 614 disposedtherebetween, and flange 624. First canned portion 602 is joined tosecond canned portion 604 using the ADRW method. In joining first cannedportion 602 to second canned portion 604, ribbed portion 618 of firstcanned portion abuts flange 624 of second canned portion 604. Flange 624comprises a mating surface sufficient for an electrode (not shown) toapply a pressure to create deformation during the ADRW welding method.Moreover, this method allows for spinforming of snorkel ends or deepdrawn shell halves. Shells 612 integrally transition into end coresforming concentric openings 622.

Further embodiments are envisioned, where the two part converter withcentral weldment may be used to create a converter that has inlet andoutlet angles to the centerline of the part. First, a shell tube is cutat half the desired angle between snorkels. New tube ends are thenformed to add features that facilitate the ADRW method (e.g., ribportion and/or flange). The tube sections are stuffed with catalyst inmat support and then joined together again after being rotated 180degrees. This process produces a converter that has an angled body withthe angle equal to about 2 times the original angle cut in the tube.This embodiment may be useful for close packaging in under hood and/orunderbody areas. Embodiments are also envisioned where greater than twocatalysts are canned separately and joined together using the ADRWmethod. The advantage of this type of construction is that each catalystis individually stuffed into each container, which may eliminate thepotential for high mat density caused by face angles between adjoiningcatalysts leading to potential breakage of the catalyst.

The same type of weld interface used in the ADRW method to formconverter to tube joints, cone to shell joints, and the like may also beused for tube to tube joins. For example, in tube-to-tube joints, afirst tube comprises a rib portion and second tube comprises a flange.

Catalyst substrate 12 comprises any ceramic material or “hightemperature material” capable of operating under exhaust systemconditions, i.e., temperatures up to about 1,100° C. and exposure tohydrocarbons, nitrous oxides, carbon monoxide, carbon dioxide, and/orsulfur in, for example, a spark ignition or diesel engine environment.These high temperature materials may be ceramic, metallic foils,combinations thereof, and other materials, that are capable ofsupporting the desired catalyst coating. Some possible ceramic materialsinclude cordierite, silicon carbide, and the like, and mixtures thereof.One such material, “Cordierite”, is commercially available from Corning,Inc., Corning, N.Y..

Catalyst substrate 12 may have any geometry, which provides a sufficientsurface area for the catalyst, with a honeycomb structure beingdesirable. The honeycomb structure may have cells shaped like triangles,squares, rectangles, hexagons, octagons, diamonds and the like. Inconsideration of the tooling costs for extrusion molding or the like,however, the cells are generally square in shape. Moreover, it isdesirable that catalyst substrate 12 has the greatest number of cellsthat is structurally feasible such that the inner surface area ofcatalyst substrate 12 is maximized. The surface area of the substrateshould also be sufficient to support a sufficient amount of catalyst(s)to effectively catalyze exhaust fluid streams flowing therethrough, withthe surface area being a function of the surface design of fluidpassages, the volume of the substrate, and the effective density of thesubstrate. These parameters may be adjusted according to designspecifications, taking into account both the desired shape of thecatalytic converter and optimal paths for exhaust fluid flow.Additionally, it is desirable that catalyst substrate 12 is formed ingeometric shapes such that mat support material 14 may be wrap aroundsubstrate 12 properly without delaminating or cracking, which may occurwhen bending the material around sharp radii, e.g., radii less thanabout 25 mm.

Catalyst substrate 12 may comprise any catalyst material sufficient toconvert exhaust fluids to acceptable emission levels. Catalyst substrate12 may be wash coated and/or imbibed with a catalyst, which may comprisea high surface area material, having one or more possible catalystmaterials including noble metals such as platinum, palladium, rhodium,iridium, osmium and ruthenium; and other metals such as tantalum,zirconium, yttrium, cerium, nickel, and copper; and mixtures and alloysthereof, and other conventional catalysts.

The mat support 14 may comprise a material that enhances the structuralintegrity of the substrate by applying compressive radial forces aboutit, reducing its axial movement, and retaining it in place, isconcentrically disposed around the substrate. Mat support material 14may be a formed ceramic fiber material comprising vermiculite,refractory ceramic fibers, organic binders, combinations thereof, andthe like. Mat support material 14 may be a non-expanding ceramicmaterial, an intumescent material, or a material comprising both.Examples of non-expanding ceramic fiber material includes, but is notlimited to, ceramic materials such as those sold under the trademarks“NEXTEL” and “SAFFIL” by the “3M” Company, Minneapolis, Minn., or thosesold under the trademark, “FIBERFRAX” and “CC-MAX” by the Unifrax Co.,Niagara Falls, N.Y., and the like. Examples of intumescent ceramicmaterial include, but is not limited to, ceramic materials such as thosesold under the trademark “INTERAM” by the “3M” Company, Minneapolis,Minn., as well as those intumescents which are also sold under theaforementioned “FIBERFRAX” trademark, as well as combinations thereofand others.

The thickness of mat support material 14 may depend upon the temperatureof the exhaust fluid, as well as the application of catalytic converter.For example, the thickness of mat support material used in catalyticconverter for a spark ignition environment may differ from that used ina diesel environment. Moreover, as the exhaust fluid temperature rangeincreases, the thickness of mat material 14 may also increaseaccordingly to meet customer skin temperature requirements. Generally,the mat support material thickness is about 2 mm to about 12 mm for mostautomotive applications, within this range it is also desirable to havea thickness of about 4 mm to about 8 mm.

The choice of material for the shell 16 depends upon the type of exhaustfluid, the maximum temperature reached by the catalyst substrate, themaximum temperature of the exhaust fluid stream, and the like. Suitablematerials for the shell 16 may comprise any material that is capable ofresisting under-car salt, temperature and corrosion. For example,ferrous materials may be employed such as ferritic stainless steels.Ferritic stainless steels may include stainless steels such as, e.g.,the 400-Series such as SS-409, SS-439, and SS-441, with SS-409particularly desirable. Acceptable SS type stainless steel may includestainless steels such as those sold under the trademarks “Type S40900”by Armco, Inc., in Pittsburgh, Pa.

Possible materials for the end-cone 20 include any material capable ofmaintaining the desired structural integrity in an operating environmentconsistent with exhaust fluid treatment, e.g., temperatures up to about1,000° C., exposure to exhaust fluids, and extreme weather conditions.Although numerous materials and alloys can be employed, ferrousmaterials and alloys are typically used. High temperature, corrosionresistant, stainless steel is desirable, with stainless steel 400series, e.g., type 409 and the like, being more desirable.

Advantageously, the Annular Deformation Resistance Welding (ADRW) methodreduces weld time compared to other welding methods, e.g., MIG welding.The cycle time for ADRW is about 1 second. Therefore, an increased cellcapacity may be realized, while using approximately the same capital.The ADRW method allows the weld to be monitored to indicate quality ofthe finished product, which is advantageous in that it may reduce weldrepair, and may have potential for reducing capital expenditure forinspection equipment (e.g., elimination of leak tester). Further, weldsmade to end cones may have a greater load bearing capacity compared towelds using other methods, because full thickness materials are beingjoined, i.e., materials that have not been thinned by, for example,extrusion.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1-9. (canceled)
 10. A method of making a catalytic converter: forming ashell comprising a welding deformation detail; inserting and housing acatalyst substrate inside said shell, wherein a mat support material isdisposed between said shell and said catalyst substrate; welding an endcone comprising a flange to said shell by applying a deformation forceto said flange causing deformation of welding deformation detail. 11.The method of claim 10, wherein said rib portion is concave.
 12. Themethod of claim 10, wherein said rib portion is convex.
 13. The methodof claim 10, wherein a mat protection surface is formed by said flangeof said end cone.
 14. The method of claim 10, wherein a mat protectionsurface is formed by said rib portion of said shell.
 15. The method ofclaim 10, further comprising an inner end cone.
 16. The method of claim10, further comprising an inner end cone comprising an inner end coneflange abutted and joined to said rib portion, wherein an insulatingspace is created between said end cone and said inner end cone.
 17. Themethod of claim 16, wherein said end cone flange comprises a pluralityof tabs.
 18. The method of claim 16, wherein said insulating space isfilled with a non-expanding ceramic material, an intumescent material,or a combination of the forgoing materials. 19-23. (canceled)
 24. Amethod of making a catalytic converter comprising the steps of: forminga generally cylindrical shell defining a characteristic line ofelongation, said shell having at least one open end concentricallydisposed on said line of elongation and an integrally formed weldingdeformation detail disposed adjacent said opening, said weldingdeformation detail including a radially distended circumferential ribportion; inserting and housing a catalyst substrate inserted within saidshell; inserting and housing mat support material between said catalystsubstrate and said shell; forming an end cone; aligning said end coneconcentrically with the opening of said shell, said end cone defining agenerally radially extending circumferential flange configured tosubstantially matingly abut said rib portion; applying a deformationforce about the circumference of said flange to simultaneously effectdeformation of said welding deformation detail about the entirecircumference thereof; and forming a single circumferentially continuousdeformation weldment interconnecting said end cone flange with thedistended rib portion of said welding deformation detail simultaneouslyabout the entire circumference thereof.